A thermoformer or thermoforming machine typically has a series of stages that transform input plastic material into finished containers. The input material is a thermoplastic substance that can be formed when heated. A common thermoplastic material is polypropylene. The finished containers are commonly used to hold food or beverages, and may be formed into a variety of sizes and shapes depending on the thermoforming process that is utilized.
Thermoplastic materials may be fed into a thermoforming machine in the form of a continuous sheet or as individually cut blanks or billets. When the input materials are individual thermoplastic billets, the process is called “scrapless thermoforming” because the finished containers need not be cut from the sheet after forming, reducing the amount of scrap material. In scrapless thermoforming, a billet feeding unit is typically used to load individual billets onto a conveying device in the machine.
Prior to being formed into containers, the billets must be heated to the desired temperature. The desired temperature depends on  the structure of the machine being used as well as the desired properties of the end product. For example, containers may be formed while the thermoplastic material is below the crystalline melt point of the material. Such forming is known as solid-phase pressure forming. Other methods involve heating the material to its melting point prior to forming. Such a process is known as melt-phase thermoforming.
A conventional scrapless thermoforming machine has several stages used to create formed containers. First, the billets are loaded into the machine. Second, an oven is used to heat the billets to the desired temperature. Third, a form station or form press utilizes a hydraulic press or other suitable means to form the individual containers. After exiting the form press, the formed containers are removed from the machine at an unloading station. Other stations may be added to the thermoforming machine as desired, such as a pre-heating oven and a coining press to form an initial container edge prior to entry into the main oven. A conveyor is typically used to transport the billets through the various stations.
Whether the containers are formed utilizing solid-phase forming or melt-phase forming, a problem that must be addressed involves the deformation of the thermoplastic material as it is heated. Because the billets are typically supported in a horizontal fashion with only peripheral supports beneath each billet due to the configuration of the form press, the billets tend to sag or droop between the supports when heated. In some cases, the billets may entirely fall out of their supports when heated due to the material deformation.
The thermoforming art has tried many methods of preventing material deformation from adversely impacting the thermoforming process. One method involves minimizing the size of the billets. This method prevents the formation of larger containers. Another  method is to utilize round billets such that the resultant uniform deformation allows the support to retain the billet during heating. This method precludes the forming of containers having a non-uniform cross-section, such as rectangular or oval containers. Yet another method of addressing the deformation issue is to utilize a ring placed on top of the billet to strengthen the frictional grip on the billet during heating. This method presents additional manufacturing challenges with respect to how to efficiently place individual rings on top of each billet during the loading process.
Accordingly, there is a need for a thermoforming machine that addresses the problem of billet deformation. Further, it would be advantageous to have a solution for the billet deformation problem that permits the formation of larger sized containers or containers having non-uniform shapes. Further still, it would be advantageous to address the problem of billet deformation without adversely impacting the efficiency of the overall processor requiring additional equipment and components.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.